On May 8, 2013, about 1930 central daylight time, an Air Tractor, Inc. AT-302, N3650B, impacted terrain during a forced landing to a field while on approach to Chambers County Airport (T00) Anahuac, Texas. The airplane experienced a total loss of engine power during cruise flight. The airplane sustained substantial damage to the fuselage. The pilot was uninjured. The airplane was registered to and operated by Airborn AG Services Inc. under 14 Code of Federal Regulations Part 91 as a business flight that was not operating on a flight plan. Visual meteorological conditions prevailed for the flight that departed from Slidell Airport (ASD), Slidell, Louisiana, and was destined to Chambers County-Winnie Stowell Airport (T90), Winnie, Texas. A ASD fixed base operator (FBO) employee stated that about 1700, he received a call from the pilot stating he needed fuel for his airplane. The FBO employee arrived about 1730 and saw that the airplane was still running. He asked the pilot to shut down the airplane, but the pilot said he could not since it would not start without an auxiliary power unit. The pilot told him to top off the airplane and went inside the FBO. As the FBO employee refueled the airplane, fuel started coming out of the fuel tank filler port and was being blown by the propeller. The FBO employee confirmed the fuel tanks were full and placed the fuel caps on. The airplane was fueled with 88 gallons, 44 gallons per side. The FBO employee went back into the FBO where he saw the pilot unplug his iPad. The FBO employee said that the pilot told him that his navigation equipment was inoperative and was using his iPad for navigation. The pilot took off about 1830 hours. In a written statement, the pilot stated the Air Tractor, Inc. AT-302 fuel system was gravity fed to a center, low-mounted, header tank that was supplied by both left and right fuel tanks. The airplane was equipped with a fuel valve that provided only on/off selections and did not provide left/right fuel tank selections. The pilot said that he had operated the airplane in Florida for the past few months. He stated that the left fuel tank always fed faster; therefore, on spray operations, fuel was just added to the left fuel tank to maintain enough fuel for each spray load. Often times the fuel tank gauge would indicate a lower fuel quantity in the left fuel tank than in the right fuel tank, and upon fueling he would find this to always be the case. He stated that the normal average fuel consumption "working hard" was about 40 gallons per hour. The total fuel capacity was 126 gallons (63 gallons per tank) in addition to the header tank. The pilot said he was delivering the airplane to Anahuac, Texas. He said that that he planned the flight with 3 hours of usable fuel or 2 ½ hours with a safety factor. He departed from ASD with full fuel, for a 300 mile/2 hour flight. The pilot stated that during the flight, he noticed that fuel was not being consumed as usual, faster from the left fuel tank. During the flight he checked the right fuel tank quantity by using the single fuel gauge, which displayed fuel for either fuel tank by selecting the respective fuel tank. He said he was concerned and surprised to see the right fuel tank indicated a fuel quantity that was lower than the left fuel tank. He said that he immediately made plans to end the flight short of his destination of T90 to check the airplane or add fuel. He was 8 minutes from T90 when he approached Chambers County Airport (T00) Anahuac, Texas, which was about 12.5 nautical miles east of T90. He approached T00 from the north for a short final approach to runway12/30 (3,005 feet by 60 feet, asphalt). He rolled slightly right and away from the interstate and then rolled slightly left as he applied flaps to slow the airplane for touchdown. The engine experienced a total loss of engine power, and the airplane sink rate "surprised" the pilot. The pilot realized that the runway was too far, so he chose to land on a cow pasture on the north side of the interstate. The airplane left wing struck the ground, and the left main landing gear broke off. The airplane slid to a stop in less 100 than feet. The pilot believed that the engine lost power because of fuel cavitation and/or starvation from unequal fuel quantities. A Federal Aviation Administration inspector stated that the pilot reported he was about 20 minutes east of T00 when the right fuel gauge indicated empty. He rocked the airplane, got a fuel indication, and continued the flight. Post-accident examination of the airplane revealed there was no usable fuel in the right wing fuel tank and about 22.9 gallons of fuel in the left wing fuel tank. There was no contamination noted within the fuel supply. Air Tractor, Inc. issued Service Letters #178 and #178A in 1999 to advise operators of fuel imbalance that could lead to fuel starvation. The Service Letters were reissued in 2002, 2004, and 2009. A warning placard was never incorporated on AT-302 airplanes, only on later models. There is also no warning in the AT-302 flight manual. A National Transportation Safety Board Pilot/Operator Aircraft Accident/Incident Report was not received from the pilot.